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OTs > JP2 > Day 1 - Day 2 (A1 - A2 - B1 - B2 - C1 - C2 - E1- E2 - E3 - F3)- Day 3
Japan Column
August 17, 2010 (Last update: Dec. 28, 2010)
JSM 7th Annual Conference at Omaezaki, Shizuoka

Day Two (July 14, 2010)

[B-2] Maintenance Optimization

Chair: Makoto TAKAHASHI (Tohoku Univ.), Hidetada MASUI (Tokyo Electric Power), Kouichi YOSHIZAWA (Kansai Electric Power)

Various contexts from on maintenance optimization in NPPs and thermal power plants, to on the influence by noises to maintenance personnel were introduced.


Study on how to evaluate the effectiveness of maintenance activities for giant complex plant system

Takayuki AOKI (Tohoku University)

If we try to check the effectiveness of maintenance activities in nuclear power plant, it is necessary to evaluate plant performance from the viewpoint of nuclear safety and economy. So, in this paper, after the relation among maintenance optimization, maintenance performance targets, maintenance effectiveness indicator and maintenance key parameters important to nuclear safety and economy was made clear, a method to evaluate the effectiveness of maintenance activities was discussed. As a result of consideration, it was concluded that the maintenance effectiveness indicator proposed in this paper can evaluate maintenance effectiveness and can show the direction of improving existing maintenance program because the relation with maintenance performance target and maintenance key parameters is clear.

Maintenance Cycle, Maintenance Optimization, Performance Indicator, Maintenance Performance Target, Maintenance Effectiveness, Maintenance Importance


System reliability comparison for operating state from both Generation Loss and Core Damage Frequency


Recently, Introduction of the use of risk information into safety related activities in nuclear power plants is being discussed by electric power companies and others. Then, as an example of "Use of Risk information", Reliability comparisons of Motor-Generator set and Variable Voltage Variable Frequency for Primary Loop Recirculation System (PLR) are simply evaluated from both Generation Loss and Core Damage Frequency (CDF) using Probabilistic Safety Assessment (PSA) in this study.

Probabilistic Safety Assessment (PSA), Generation Risk Assessment (GRA), Core Damage Frequency (CDF), Primary Loop Recirculation System (PLR)


Overview of the technical evaluation of 40-year Plant Life Management Tsuruga Power Station unit 1

Tamotsu TSUDA, Takehiro KUSUNOKI, Hiroshi OKADA, Takeshi YAMADA (The Japan Atomic Power Company)

Japan Atomic Power Company (JAPC) has completed the Ageing Management Technical Evaluation (AMTE) for Tsuruga Power Station unit 1 that has entered 40-year operation first in Japan, and has established the long-term maintenance management policy based on the evaluation.

JAPC conducted the AMTE in accordance with "Ageing Management Implementation Guideline for Nuclear Power Plants", "Code on Implementation and review of Nuclear Power Plant Ageing Management Programs 2008" etc. During the 40-years AMTE, the verification of the 30 years AMTE results was also performed as an additional evaluation to 30 years AMTE.

The AMTE of Tsuruga Power Station unit 1 concluded that most of component and structure would be maintained their integrity by continued existing preservation activities, even assuming the operation period of 60 years.

For some components, JAPC identified additional maintenance activities to be implemented after 40 years operation as a part of the long term maintenance policy. These activities will be reflected in maintenance plan and implemented, which assure the integrity of these component.

PLM, Ageing management technical evaluation (AMTE), 40-year, Tsuruga, JAPC

Approaches to extend operating cycle of Hamaoka Unit 3

Youzou ISHIGAMI, Toshihiro KODAKA, Michita MIZUNO and Tadayuki SANO (CHUBU Electric Power Co., lnc.)

The new regulatory requirements for inspections at nuclear power station took effect in January 2009, which require utilities to enhance an optimization of maintenance programs. At the same time, this regulatory change made it possible for utilities to apply for an extension of the operating cycle of a plant from 13 months of previous regulatory limit up to 24 months.

In this paper, approaches to extend operating cycle of Hamaoka Unit 3 are described.

New Nuclear Inspection System, Maintenance activities, Technical Assessment, Hamaoka Unit 3


Preliminary Evaluation Results on the Effects of Power Uprate upon Maintenance Activities

Hitoshi OHATA, Yuji MUROI, and Tetsuya ONOSE (The Japan Atomic Power Company)

The Japan Atomic Power Company (JAPC) plans to increase rated reactor thermal power of Tokai No.2 Power Station (Tokai-2) by five percent. This paper describes preliminary evaluation results on the effects of five-percent power uprate in Tokai-2 upon its maintenance activities.

Tokai-2, Power Uprate, Aging degradation Mechanism, Plant Life Management, Maintenance Activity


The Reflection of Operation and Maintenance Experience to the First Advanced PWR Design

Tomohiko HOSHINO and Kimihito TAKEUCHI (The Japan Atomic Power Company)

Tsuruga Unit 3&4 is the first APWR, which introduces a lot of improved technology aiming at safety, reliability and operability enhancement. This paper explains about our activities as to the reflection of our operation and maintenance experience including countermeasures against experienced troubles and plant life management evaluation result of operating PWRs in Japan. And the preparation for maintenance program introduction and basic policy for training of future operators and maintenance engineers are also described briefly.

Advanced PWR, Tsuruga unit 3&4, Reflection of Operation and Maintenance Experience


Research and Evaluation of New Technologies to Improve the Maintenance of Pipeline for Gas Distribution toward the Next Generation

Yuji HIGUCHI (The Japan Gas Association), Tetsuya KIBAYASHI (Hokkaido Gas Co., Ltd.), Tadahito SIRATO (KEIYOGAS Corporation), Takahiro SHIGETA, Masaaki ISHIKAWA, Yishikazu HASHIMOTO (Tokyo Gas Co., Ltd.), Tsuyoshi WATANABE (SHIZUOKA GAS Co., Ltd.), Toshio HIRAI, Toshiaki ADACHI, Motoki KUWAHARA (TOHO GAS CO.,LTD.), Keisuke NAGASAWA, Masaru TSUNASAKI (Osaka Gas Co.,Ltd.), Yoshirou BIWATOMO (HIROSHIMA GAS Co., Ltd. ), Toshiaki FURUNO (Saibu Gas Co., Ltd.)

The aim of this study is to research and evaluate new technologies in the world from the point of view to improve the safety and security of pipeline for gas distribution toward the next generation which can practice the productive maintenance and preventive maintenance.

Maintenance, Pipeline, Gas Distribution, New technologies


Establishment of an In-House Technique for Maintaining Circuit Breakers Used in Aging Power Plants

Kiyotaka MURAKAMI and Hiroyuki MORITA (CHUBU Electric Power Co., lnc.)

In a thermal power plant that has been operating for more than 30 years, approximately 1100 MBBs and ACBs are used. However, since the supply of substitution parts from the breaker manufacturer stopped in 2005 and maintenance has become difficult, Chubu Electric has established an in-house maintenance technique through technical collaboration with its group company Chubu Plant Service Co., Ltd., in order for the company to be independent of the manufacturer.

Establishment of an In-House Technique


High noise effects on engineers' sound perception: improving listening capabilities in noisy environments

Ryuichi KIMURA and Keita KONDO (Kobe University)

In a ship’s engine room, engineers are surrounded by various noises emitted from the diesel engine, generator, pumps, and other auxiliary machines. During inspections and activities in such environments, workers strive to listen for extraordinary noises issuing from machines and instruments, which might signal a need for maintenance work. If that practice functions well, proper noise perception helps them perform maintenance work and achieve early detection of abnormalities that would otherwise contribute to ship accidents.

We specifically examined the listening capabilities used to detect extraordinary noises in noisy conditions such as those in engine rooms. This study investigated natural human capabilities and administered a questionnaire survey of machine room workers. Examinees were asked to tell the direction from which a certain sound came. Fewer questions were answered correctly in noisy conditions: 20% fewer than with no background noise. Results underscore the difficulty of discerning the correct direction from whence sound comes, signaling a deficit of hearing sensitivity. We propose a support system to improve acoustic sensing in noisy conditions. The system’s performance was evaluated, revealing a definite improvement in perception of sound information in noisy conditions at around 100 dB, which are typical of a diesel engine room.

noisy environments ,direction, listening capabilities


Arrest of SCC, Fatigue and Hydrogen Assisted Cracks, and Make Harmless the Cracks by Overload

Kotoji ANDO, Koji TAKAHASHI (YOKOHAMA National University), Keiji HOUJYOU (Oyama National College of Technology), Yasuaki HASHIKURA, Hiroshi MIZUKAMI, Hayato SANO (YOKOHAMA National University)

This study proposes an innovative method for arresting SCC, fatigue and hydrogen assisted cracks, and making harmless the cracks by overload. By overloading, compressive residual stress is introduced ahead of the crack. The residual stress reduce K values and arrest the crack. By theory, K1SCC, K1HE and ⊿Kth increase with increasing Kov (K value by overload) and the nominal threshold values were given the equation: NK1SCC, NK1HE and ⊿NKth=C + DKov. Where C is K1SCC, K1HE and ⊿Kth, respectively、and D is a proportional constant and 0.24 ~0.27. Experimental results showed that D showed good agreement with theory, except SUS316 steel by SCC. The reason was assumed that SCC test time for K1SCC definition was not enough but shorter. If threshold vales are enough larger than applied K and ⊿K values, crack is able to grow and can be made harmless.

Overload Effect, SCC, Fatigue, Hydrogen Assisted Crack, Crack Arrest, Make Crack Harmless


Maintenance activities in Chemical Processing Facility
1. Renewal of driving unit of negative pressure control valves

Yuki KOBAYASHI, Teturo TAKAHASHI, Tadahiro SHINOZAKI, Kouji OGASAWARA, Kenji KOIZUMI, and Yasuo NAKAZIMA (Japan Atomic Energy Agency)

The negative pressure control valve is reliable apparatus which has been used in many nuclear facilities. In recent years, there are some troubles on those valves in CPF (Chemical Processing Facility) by the aged deterioration because the valves were kept using for more than 25 years after facility had operated. Therefore, we have been carrying out renewal of driving units of the valves to assure performance of negative pressure control function and to keep stability of operation of the facility. In this presentation, we report knowledge provided through the renewal work, such as the renewal procedure, the deterioration situation of components and the cause of troubles.

Chemical Processing Facility, aged deterioration, negative pressure control valve


The lube oil leakage from indicator valves of Emergency Diesel Generator

Masaru KURATA, Masaru MIZUKAMI, Takeshi NISHITA and Keiichiroh TATEKABE (Hokuriku Electric Power Company)

The lube oil leakage from indicator valves of Emergency Diesel Generator was found at Shika nuclear power plant Unit 2 in Dec. 2009.

As a result of investigation, we found that temperature fall after shutdown of diesel engine generate negative pressure in the combustion chamber, and the cooling oil for piston leak into the combustion chamber through the oil-drain port of piston by this negative pressure.

Emergency Diesel Generator,Diesel engine


Study of Degradation of Off-Gas H2/O2 Recombination Catalyst at Hamaoka Unit 4 and 5

Hiroyasu OOSUMI, Seishi MUTO (CHUBU Electric Power Co., lnc.), Kenichi KAWABE and Toru KAWASAKI (Hitachi-GE Nuclear Energy, Ltd.)

By evaluating the phenomena that hydrogen concentration of outlet gas in the off-gas treatment system at Hamaoka Unit 4 and 5 had increased, it was concluded that the causes of the phenomena were transformation of support alumina by alteration of manufacturing process of catalysts and the deactivation by catalyst poisoning material. Therefore, the manufacturing process was modified and the poisoning material was identified and removed. Moreover, developments such as catalyzer performance monitoring technology with thermometers have been continued in order to improve the reliability of the system.

Catalyst, Off-Gas System, Recombiner Degradation, Boehmite, Organic Silicon


The construction of an intensive monitoring system for power supply stations in the Tokai Reprocessing Plant

Kenji AOKI, Hisao HIYAMA, Satomi SHIBATA, Shogo IWASAKI and Shinichi INAMI (Japan Atomic Energy Agency)

There are plural facilities having a radiation controlled area in the Tokai reprocessing plant, and an uninterruptible power supply system which considered a blackout is necessary for the power supply to each facility from the viewpoint of radiological management and nuclear material containment. In addition, at the time of the power supplying abnormality, intelligence gathering is necessary for prompt measures and restoration. In this report, the intensive monitoring system, which aimed for the unification of the power supply monitor place and the acceleration of the intelligence gathering to detect a power supply abnormality point, is described.

uninterruptible power supply, intensive monitoring system, reprocessing plant


Optimization of the exchange period of high efficiency particulate air filter in Tokai Reprocessing Plant

Hiroyuki KAWASUMI, Hirotaka SANYOSHI, Hideo YATOGI, Yoshihiro FUKUARI, Shinichi INAMI (Japan Atomic Energy Agency)

In the ventilation facilities of the Tokai reprocessing plant, particle filters are generally installed both in air-intake and exhaust systems. In the air-intake system, atmospheric dust is filtered and the cleaned air is supplied into radiation controlled areas, whereas in the exhaust system, radioactive materials are filtered and it is discharged to the environment. Because the filter of the exhaust system serves to prevent radiological release to the environment, a high-efficiency particle air (HEPA) filter that a decontamination factor is extremely high, is used for filtering radioactive particles. The HEPA filter is usually exchanged with new one when the filter is carried over with particles, or it is exchanged by the limit as an anti-aging deterioration measure in time.

This report reviews the exchange period of a particle filter by confirming the integrity of a filter installed in investigation and the enforcement of the past filter exchange results and reports the result that planned adequacy.

Tokai Reprocessing Plant, ventilation facilities, HEPA filter, exchange period

Application RiskWatcher to Japanese PWR

Hiromichi TAKAHASHI, Tetsuro YAMAMOTO (Mitsubishi Heavy Industries, LTD.), Futoshi TANAKA (Mitsubishi Nuclear Energy Systems)

On-Line-Maintenance (OLM) of NPP is under discussion for introduction of in Japan. Risk monitor is a real-time risk analysis tool used to determine the point-in-time risk based on the actual plant configuration, which assess increase in risk that may result from OLM activities. MHI adopted RiskWatcherTM provided by Swedish company Scandpower as risk monitor software and is developing it for Japanese utilities application. By Inputting PSA model into RiskWatcherTM, the risk-monitor is made up. It can calculate the risk level (Core Damage Frequency and Containment Failure Frequency), importance factors, and Defence-in-Depth of NPP at a short time so that it may contribute effective planning schedule of OLM.

Living PSA, risk monitor, RiskWacher, Riskspectrum, On-Line-Maintenance


Fig. 8 A presentation on [B-2] "Maintenance Optimization"

Proceedings of JSM 7th Annual Conference, p.121-p.183, Omaezaki, July 2010 (in Japanese).

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